Integrating passive devices in package structures

ABSTRACT

A method includes bonding a first device die with a second device die. The second device die is over the first device die. A passive device is formed in a combined structure including the first and the second device dies. The passive device includes a first and a second end. A gap-filling material is formed over the first device die, with the gap-filling material including portions on opposite sides of the second device die. The method further includes performing a planarization to reveal the second device die, with a remaining portion of the gap-filling material forming an isolation region, forming a first and a second through-vias penetrating through the isolation region to electrically couple to the first device die, and forming a first and a second electrical connectors electrically coupling to the first end and the second end of the passive device.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a divisional of U.S. patent application Ser. No.16/028,763, entitled “Integrating Passive Devices in PackageStructures,” filed on Jul. 6, 2018, which claims the benefit of theProvisional Application No. 62/586,333, filed Nov. 15, 2017, andentitled “Integrating Passive Devices in SoIC Structures;” whichapplications are hereby incorporated herein by reference.

BACKGROUND

The packages of integrated circuits are becoming increasing complex,with more device dies packaged in the same package to achieve morefunctions. For example, a package structure has been developed toinclude a plurality of device dies such as processors and memory cubesin the same package. The package structure can include device diesformed using different technologies and have different functions bondedto the same device die, thus forming a system. This may savemanufacturing cost and optimize device performance.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1 through 10 are cross-sectional views of intermediate stages inthe manufacturing of a package in accordance with some embodiments.

FIGS. 11 through 13 illustrate the cross-sectional views of packageshaving device dies bonded through face-to-face bonding in accordancewith some embodiments.

FIG. 14 illustrates the cross-sectional view of a package having devicedies bonded through face-to-back bonding in accordance with someembodiments.

FIGS. 15 and 16 illustrate exemplary passive devices in accordance withsome embodiments.

FIGS. 17 and 18 illustrate exemplary passive devices formed in ashielding structure in accordance with some embodiments.

FIGS. 19 and 20 illustrate the cross-sectional views of packagesembedding packages in accordance with some embodiments.

FIG. 21 illustrates a process flow for forming a package in accordancewith some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “underlying,” “below,”“lower,” “overlying,” “upper” and the like, may be used herein for easeof description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

A package and the method of forming the same are provided in accordancewith various exemplary embodiments. The intermediate stages of formingthe package are illustrated in accordance with some embodiments. Somevariations of some embodiments are discussed. Throughout the variousviews and illustrative embodiments, like reference numbers are used todesignate like elements.

FIGS. 1 through 10 illustrate the cross-sectional views of intermediatestages in the formation of a package in accordance with some embodimentsof the present disclosure. The steps shown in FIGS. 1 through 10 arealso reflected schematically in the process flow 200 shown in FIG. 21.

FIG. 1 illustrates the cross-sectional view in the formation of packagecomponent 2. In accordance with some embodiments of the presentdisclosure, package component 2 is a device wafer including activedevices 22 such as transistors and/or diodes, and possibly passivedevices such as capacitors, inductors, resistors, or the like. Packagecomponent 2 may include a plurality of chips 4 therein, with one ofchips 4 illustrated. Chips 4 are alternatively referred to as (device)dies hereinafter. In accordance with some embodiments of the presentdisclosure, device die 4 is a logic die, which may be a CentralProcessing Unit (CPU) die, a Micro Control Unit (MCU) die, aninput-output (IO) die, a BaseBand (BB) die, an Application processor(AP) die, or the like. Device die 4 may also be a memory die such as aDynamic Random Access Memory (DRAM) die or a Static Random Access Memory(SRAM) die, or may be other types of dies. In subsequent discussion, adevice wafer is discussed as an exemplary package component 2. Theembodiments of the present disclosure may also be applied to other typesof package components such as interposer wafers.

In accordance with some embodiments of the present disclosure, theexemplary wafer 2 includes semiconductor substrate 20 and the featuresformed at a top surface of semiconductor substrate 20. Semiconductorsubstrate 20 may be formed of crystalline silicon, crystallinegermanium, crystalline silicon germanium, and/or a III-V compoundsemiconductor such as GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, GaInAsP, orthe like. Semiconductor substrate 20 may also be a bulk siliconsubstrate or a Silicon-On-Insulator (SOI) substrate. Shallow TrenchIsolation (STI) regions (not shown) may be formed in semiconductorsubstrate 20 to isolate the active regions in semiconductor substrate20. Although not shown, through-vias may be formed to extend intosemiconductor substrate 20, and the through-vias are used toelectrically inter-couple the features on opposite sides of wafer 2.

In accordance with some embodiments of the present disclosure, wafer 2includes integrated circuit devices 22, which are formed on the topsurface of semiconductor substrate 20. Exemplary integrated circuitdevices 22 may include Complementary Metal-Oxide Semiconductor (CMOS)transistors, resistors, capacitors, diodes, and/or the like. The detailsof integrated circuit devices 22 are not illustrated herein. Inaccordance with alternative embodiments, wafer 2 is used for forminginterposers, in which substrate 20 may be a semiconductor substrate or adielectric substrate.

Inter-Layer Dielectric (ILD) 24 is formed over semiconductor substrate20, and fills the space between the gate stacks of transistors (notshown) in integrated circuit devices 22. In accordance with someexemplary embodiments, ILD 24 is formed of Phospho Silicate Glass (PSG),Boro Silicate Glass (BSG), Boron-Doped Phospho Silicate Glass (BPSG),Fluorine-Doped Silicate Glass (FSG), Tetra Ethyl Ortho Silicate (TEOS),or the like. ILD 24 may be formed using spin coating, Flowable ChemicalVapor Deposition (FCVD), Chemical Vapor Deposition (CVD), PlasmaEnhanced Chemical Vapor Deposition (PECVD), Low Pressure Chemical VaporDeposition (LPCVD), or the like.

Contact plugs 28 are formed in ILD 24, and are used to electricallyconnect integrated circuit devices 22 to overlying metal lines 34 andvias 36. In accordance with some embodiments of the present disclosure,contact plugs 28 are formed of a conductive material selected fromtungsten, aluminum, copper, titanium, tantalum, titanium nitride,tantalum nitride, alloys therefore, and/or multi-layers thereof. Theformation of contact plugs 28 may include forming contact openings inILD 24, filling a conductive material(s) into the contact openings, andperforming a planarization (such as Chemical Mechanical Polish (CMP)process) to level the top surfaces of contact plugs 28 with the topsurface of ILD 24.

Over ILD 24 and contact plugs 28 resides interconnect structure 30.Interconnect structure 30 includes dielectric layers 32, and metal lines34 and vias 36 formed in dielectric layers 32. Dielectric layers 32 arealternatively referred to as Inter-Metal Dielectric (IMD) layers 32hereinafter. In accordance with some embodiments of the presentdisclosure, at least a lower layer in dielectric layers 32 is formed ofa low-k dielectric material having a dielectric constant (k-value) lowerthan about 3.0 or lower than about 2.5. Dielectric layers 32 may beformed of Black Diamond (a registered trademark of Applied Materials), acarbon-containing low-k dielectric material, Hydrogen SilsesQuioxane(HSQ), MethylSilsesQuioxane (MSQ), or the like. In accordance withalternative embodiments of the present disclosure, some or all ofdielectric layers 32 are formed of non-low-k dielectric materials suchas silicon oxide, silicon carbide (SiC), silicon carbo-nitride (SiCN),silicon oxy-carbo-nitride (SiOCN), or the like. In accordance with someembodiments of the present disclosure, the formation of dielectriclayers 32 includes depositing a porogen-containing dielectric material,and then performing a curing process to drive out the porogen, and hencethe remaining dielectric layers 32 becomes porous. Etch stop layers (notshown), which may be formed of silicon carbide, silicon nitride, or thelike, are formed between IMD layers 32, and are not shown forsimplicity.

Metal lines (also include metal pads) 34 and vias 36 are formed indielectric layers 32. The metal lines 34 at a same level arecollectively referred to as a metal layer hereinafter. In accordancewith some embodiments of the present disclosure, interconnect structure30 includes a plurality of metal layers that are interconnected throughvias 36. Metal lines 34 and vias 36 may be formed of copper or copperalloys, and they can also be formed of other metals. The formationprocess may include single damascene and dual damascene processes. In anexemplary single damascene process, a trench is first formed in one ofdielectric layers 32, followed by filling the trench with a conductivematerial. A planarization process such as a CMP process is thenperformed to remove the excess portions of the conductive materialhigher than the top surface of the IMD layer, leaving a metal line inthe trench. In a dual damascene process, both a trench and a via openingare formed in an IMD layer, with the via opening underlying andconnected to the trench. The conductive material is then filled into thetrench and the via opening to form a metal line and a via, respectively.The conductive material may include a diffusion barrier and acopper-containing metallic material over the diffusion barrier. Thediffusion barrier may include titanium, titanium nitride, tantalum,tantalum nitride, or the like.

Metal lines 34 include metal lines 34A, which are sometimes referred toas top metal lines. Top metal lines 34A are also collectively referredto as being a top metal layer. The respective dielectric layer 32A maybe formed of a non-low-k dielectric material such as Un-doped SilicateGlass (USG), silicon oxide, silicon nitride, or the like. Dielectriclayer 32A may also be formed of a low-k dielectric material, which maybe selected from the similar materials of the underlying IMD layers 32.

In accordance with some embodiments of the present disclosure,dielectric layers 38, 40, and 42 are formed over the top metal layer.Dielectric layers 38 and 42 may be formed of silicon oxide, siliconoxynitride, silicon oxy-carbide, or the like, Dielectric layer 40 isformed of a dielectric material different from the dielectric materialof dielectric layer 42. For example, dielectric layer 42 may be formedof silicon nitride, silicon carbide, or the like.

Vias 44 and metal pads 46A, 46B, and 46C are formed in dielectric layers38, 40, and 42. The respective process is illustrated as step 202 in theprocess flow shown in FIG. 21. Metal pads 46A, 46B, and 46C may becollectively and individually referred to as metal pads 46 hereinafter.Vias 44 and metal pads 46 may be formed using a dual damascene process,which includes forming via openings in dielectric layers 38 and 40,trenches in dielectric layer 42, and filling the via openings andtrenches with conductive materials. A planarization process such as aCMP process or a mechanical grinding process is performed to level thetop surfaces of dielectric layer 42 and metal pads 46. The filling ofthe conductive materials may include depositing a diffusion barrier suchas a titanium nitride layer, a tantalum nitride layer, a titanium layer,a tantalum layer, or the like, and depositing a copper-containingmaterial over the diffusion barrier.

Device die 4 may also include metal pads such as aluminum or aluminumcopper pads, which may be formed in dielectric layer 38 in accordancewith some embodiments. The aluminum (copper) pads are not shown forsimplicity.

In accordance with some embodiments of the present disclosure, there isno organic dielectric material such as polymer layer in wafer 2. Organicdielectric layers typically have high Coefficients of Thermal Expansion(CTEs), which may be 10 ppm/C° or higher. This is significantly greaterthan the CTE of silicon substrate (such as substrate 20), which is about3 ppm/C°. Accordingly, organic dielectric layers tend to cause thewarpage of wafer 2. Not including organic materials in wafer 2advantageously reduces the CTE mismatch between the layers in wafer 2,and results in the reduction in warpage. Also, not including organicmaterials in wafer 2 makes the formation of fine-pitch metal lines (suchas 66 and 70 in FIG. 10) and high-density bond pads possible, andresults in the improvement in the routing ability.

FIG. 1 also illustrates the formation of passive device 48A, which isformed simultaneously with the formation of the top metal layer andmetal pads 46. Throughout the description, passive devices may beidentified as 48A, 48B, 48C, 48D, 48E, 48F, 48G (shown in FIGS. 10through 14), or the like, which may be collectively and individuallyreferred to as passive devices 48. In accordance with some embodimentsof the present disclosure, passive device 48A (and any other passivedevice 48) may be a capacitor, an inductor, a transformer, a resistor,or the like. FIG. 15 illustrates an exemplary passive device 48, whichis a capacitor. Capacitor 48 includes capacitor plates 160 and 164 andcapacitor insulator 162. Capacitor plates 160 and 164 are also referredto as the two terminals TB and TA, respectively, of capacitor 48. Whencapacitor 48A (FIG. 1) is a capacitor having the structure shown in FIG.15, the top capacitor plate 164 is formed simultaneously as metal pads46 (FIG. 1), the bottom capacitor plate 160 is formed simultaneously astop metal layer 34A (FIG. 1), and the capacitor insulator is a part ofdielectric layers 38 and 40.

FIG. 16 illustrates an exemplary passive device 48, which is aninductor. The inductor may include bottom plates 166, top plates 170,and vias 168. Vias 168 interconnect bottom plates 166 and top plate 170to form the inductor. When capacitor 48A (FIG. 1) is an inductor havingthe structure shown in FIG. 16, the top plates 170 are formedsimultaneously as metal pads 46, the bottom plates 166 are formedsimultaneously as top metal layer 34A, and vias 168 (FIG. 16) are formedsimultaneously as vias 44 (FIG. 1). Passive device 48 in FIG. 16 alsohas two terminals TA and TB. Throughout the description, more passivedevices may be formed, and the exemplary structures and thecorresponding layers may be found by referring to FIGS. 15 and 16 asexamples. It is appreciated that the passive devices may have manydifferent structures than what are shown in FIGS. 15 and 16.

FIG. 2 illustrates the bonding of device die 112 to device die 4. Therespective process is illustrated as step 204 in the process flow shownin FIG. 21. In accordance with some embodiments of the presentdisclosure, device die 112 is a logic die, which may be a CPU die, a MCUdie, an IO die, a BaseBand die, an AP die, or the like. Device dies 112may also be a memory die. Device die 110 includes semiconductorsubstrate 114, which may be a silicon substrate. Through-Silicon Vias(TSVs) 116, sometimes referred to as through-semiconductor vias orthrough-vias, are formed to penetrate through semiconductor substrate114. TSVs 116 are used to connect the devices and metal lines formed onthe front side (the illustrated bottom side) of semiconductor substrate114 to the backside. Also, device dies 112 include interconnectstructures 130 for connecting to the active devices and passive devicesin device dies 112. Interconnect structures 130 include metal lines andvias (not shown).

Device die 112 may include dielectric layers 138 and 142, and etch stoplayer 140 between dielectric layers 138 and 142. Bond pads 146 and vias144 are formed in layers 138, 140, and 142. In accordance with someembodiments of the present disclosure, die 112 is free from organicdielectric materials such as polymers. The materials and the formationmethods of dielectric layers 138 and 142, bond pads 146, and vias 144may be similar to their corresponding parts in device die 4, and hencethe details are not repeated herein.

The bonding of device die 112 to die 4 may be achieved through hybridbonding. For example, bond pads 146 are bonded to bond pads 46A and 46Cthrough metal-to-metal direct bonding. In accordance with someembodiments of the present disclosure, the metal-to-metal direct bondingis copper-to-copper direct bonding. Bond pads 146 may have sizes greaterthan, equal to, or smaller than, the sizes of the respective bond pads46A and 46C. Although one device die 112 is illustrated, there may be aplurality of device dies 112 bonding to wafer 2, and gaps 53 are leftbetween neighboring device dies 112. Furthermore, dielectric layers 142are bonded to surface dielectric layer 42 throughdielectric-to-dielectric bonding, which may be fusion bonding, forexample, with Si—O—Si bonds generated. To achieve the hybrid bonding,device die 112 is first pre-bonded to dielectric layer 42 and bond pads46A by lightly pressing device die 112 against die 4. An anneal is thenperformed to incur the inter-diffusion of the metals in bond pads46A/46C and the corresponding overlying bond pads 146.

Referring back to FIG. 2, in accordance with some embodiments, after thebonding process, a backside grinding may be performed to thin devicedies 112, for example, to a thickness between about 15 μm and about 30μm. FIG. 2 schematically illustrates dashed line 112-BS1, which is theback surface of device die 112 before the backside grinding. Backsurface 112-BS2 is the back surface of device die 112 after the backsidegrinding. Through the thinning of device die 112, the aspect ratio ofgaps 53 is reduced in order to perform gap filling. Otherwise, the gapfilling may be difficult due to the otherwise high aspect ratio of gaps53. After the backside grinding, TSVs 116 may be revealed.Alternatively, TSVs 116 are not revealed at this time, and the backsidegrinding is stopped when there is a thin layer of substrate 114 coveringTSVs 116. In accordance with these embodiments, TSVs 116 may be revealedin the step shown in FIG. 4. In accordance with other embodiments inwhich the aspect ratio of gaps 53 is not too high for gap filling, thebackside grinding is skipped.

In accordance with some embodiments of the present disclosure, devicedie 112 includes a portion of passive device 48B. After the bonding ofdevice die 112 and device die 4, a metal pad(s) of device die 4 isbonded to the portion of passive device 48B in device die 112 to formthe entire passive device 48B. For example, when passive device 48B is acapacitor, the top capacitor plate may be a part of top metal layer134A. The bottom capacitor plate includes an upper portion and a bottomportion, which are the metal pads of device dies 112 and 4,respectively. When passive device 48B is an inductor, for example, asshown in FIG. 16, the top plates 170 (FIG. 16) will be in the top metallayer 134A (FIG. 2) in device die 112, the vias 168 (FIG. 16) will be indielectric layers 138 and 140 (FIG. 2) in device die 112, and each ofthe bottom plates 166 (FIG. 16) will also include an upper portion and abottom portion, which are the metal pads of device dies 112 and 4,respectively.

After the bonding of device die 112 to device die 4, electricalconnection channels 52 are formed, each including stacked metalpads/lines and vias, so that the passive devices 48 that are formed indevice dies 112 and 4 may be connected to the overlying electricalconnectors (such as solder regions) that will be formed in subsequentsteps. Shielding rings 50 are formed, each encircling one of theelectrical channels 52. When viewed from the top of the structure shownin FIG. 2, shielding rings 50 have the shape of rings. Shielding rings50 are formed of metal lines and vias, which may be solid rings (withoutbreaks) in some metal layers and some via layers. In order toelectrically connect to passive devices, shielding rings 50 have somebreaks allowing metal lines to pass through the breaks to connectpassive devices 48 to electrical channels 52. The metal lines thatconnect to the passive devices 48 are electrically insulated fromshielding rings by dielectric materials. For example, FIG. 10illustrates a cross-sectional view obtained from a plane in which themetal lines pass through the breaks in shielding rings 50 tointerconnect passive device 48B and electrical connection channels 52.The dashed lines (which show parts of shielding rings 50) in FIG. 10represent the parts of shielding rings in front of and behind theillustrated plane. Shielding rings 50 are electrically grounded, so thatthe passive device (such as 48B) does not interfere, and is notinterfered by, other devices in device dies 112 and 4.

FIG. 3 illustrates the formation of gap-filling layers, which includesdielectric layer 56 and the underlying etch stop layer 54. Therespective process is illustrated as step 206 in the process flow shownin FIG. 21. Dielectric layer 54 may be deposited using a conformaldeposition method such as Atomic Layer Deposition (ALD) or ChemicalVapor Deposition (CVD). Etch stop layer 54 is formed of a dielectricmaterial that has a good adhesion to the sidewalls of device dies 112,the top surfaces of dielectric layer 42, and bond pads 46B. Inaccordance with some embodiments of the present disclosure, etch stoplayer 54 is formed of a nitride-containing material such as siliconnitride. Etch stop layer 54 may be a conformal layer, with the thicknessT1A of the horizontal portions and thickness T1B of the verticalportions being substantially equal to each other, for example, with thedifference (T1A-T1B) having an absolute value smaller than about 20percent, or smaller than about 10 percent, of both thicknesses T1A andT1B.

Dielectric layer 56 is formed of a material different from the materialof etch stop layer 54. In accordance with some embodiments of thepresent disclosure, dielectric layer 56 is formed of silicon oxide,which may be formed of TEOS, while other dielectric materials such assilicon carbide, silicon oxynitride, silicon oxy-carbo-nitride, PSG,BSG, BPSG, or the like may also be used. Dielectric layer 56 may beformed using CVD, High-Density Plasma Chemical Vapor Deposition(HDPCVD), Flowable CVD, spin-on coating, or the like. Dielectric layer56 fully fills the remaining gaps 53 (FIG. 2).

Referring to FIG. 4, a planarization process such as a CMP process or amechanical grinding process is performed to remove excess portions ofgap-filling layers 54 and 56, so that device die 112 is exposed. Therespective process is also illustrated as step 206 in the process flowshown in FIG. 21. Also, through-vias 116 are exposed. The remainingportions of layers 54 and 56 are collectively referred to as(gap-filling) isolation regions 58.

In accordance with some embodiments of the present disclosure, as shownin FIG. 5, substrate 114 is lightly etched, so that through-vias 116 hasa top portion protruding out of the top surfaces of substrate 114.Dielectric layer 60 is formed, and is lightly polished to remove theportions of dielectric layer 60 covering through-vias 116. Dielectriclayer 60 may be formed of silicon oxide, silicon nitride, siliconoxynitride, or the like. In accordance with some embodiments of thepresent disclosure, the etching of through-vias 116 and the formation ofdielectric layer 60 are skipped.

FIG. 6 illustrates the etching of dielectric layers 60, 56, and 54 toform openings 61. The respective process is illustrated as step 208 inthe process flow shown in FIG. 21. In accordance with some embodimentsof the present disclosure, a photo resist (not shown) is formed andpatterned, and dielectric layers 60 and 56 are etched using thepatterned photo resist as an etching mask. Openings 61 are thus formed,and extend down to etch stop layer 54, which acts as the etch stoplayer. In accordance with some embodiments of the present disclosure,layers 60 and 56 comprise an oxide, and the etching may be performedthrough dry etching. The etching gas may include a mixture of NF₃ andNH₃, or a mixture of HF and NH₃. Next, etch stop layer 54 is etched, sothat openings 61 extend down to bond pads 46B. In accordance with someembodiments of the present disclosure, etch stop layer 54 is formed ofsilicon nitride, and the etching is performed using dry etching. Theetching gas may include a mixture of CF₄, O₂, and N₂, a mixture of NF₃and O₂, SF₆, a mixture of SF₆ and O₂, or the like.

FIG. 7 illustrates the formation of through-vias 64 (including 64-1 and64-2) and Through-Dielectric Via (TDV) 65, which fills openings 61 (FIG.6). The respective process is illustrated as step 210 in the processflow shown in FIG. 21. Through-vias 64 and TDVs 65 are connected to bondpads 46B. TDVs 65 are electrically grounded to form a shieldingstructure, so that the passive device (such as 48C in FIG. 10) does notinterfere, and is not electrically interfered by, other devices indevice dies 112 and 4. In accordance with some embodiments of thepresent disclosure, the formation of through-vias 64 and TDVs 65includes performing a plating process such as an electrical-chemicalplating process or an electro-less plating process. Through-vias 64 andTDVs 65 may include a metallic material such as tungsten, aluminum,copper, or the like. A conductive barrier layer (such as titanium,titanium nitride, tantalum, tantalum nitride, or the like) may also beformed underlying the metallic material. A planarization such as a CMPis performed to remove excess portions of the plated metallic material,and the remaining portions of the metallic material form through-vias 64and TDVs 65. Through-vias 64 and TDVs 65 may have substantially straightand vertical sidewalls. Also, through-vias 64 and TDVs 65 may have atapered profile, with top widths slightly greater than the respectivebottom widths.

In accordance with alternative embodiments, TSVs 116 are not pre-formedin device dies 112. Rather, they are formed after the formation ofisolation regions 58. For example, either before or after the formationof openings 61 (FIG. 6), device dies 112 are etched to form additionalopenings (occupied by the illustrated TSVs 116). The additional openingsin device dies 112 and openings 61 may be filled simultaneously to formthrough TSVs 116 and through-vias 64. The resulting through-vias 116 mayhave upper portions wider than the respective lower portions, oppositeto what are shown in FIG. 10.

Referring to FIG. 8, dielectric layers 62 and 63, Redistribution Lines(RDLs) 66 and 70, and vias 68 are formed. The respective process isillustrated as step 212 in the process flow shown in FIG. 21. Inaccordance with some embodiments of the present disclosure, dielectriclayers 62 and 63 are formed of an oxide such as silicon oxide, a nitridesuch as silicon nitride, or the like. Although two RDL layers areillustrated, there may be more than two layers of RDLs. RDLs 70 may beformed using single and/or dual damascene processes, which includeetching the dielectric layers to form via openings and trenches,depositing a conductive barrier layer into the openings, plating ametallic material such as copper or a copper alloy, and performing aplanarization to remove the excess portions of the metallic material.There may be etch stop layers between dielectric layers 60, 62, and 63,which etch stop layers are not shown.

FIG. 8 illustrates passive device 48C, which may also be a capacitor, aninductor, or the like, as illustrated in some exemplary embodiments inFIGS. 15 and 16. Passive device 48C is formed simultaneously with theformation of other redistribution lines.

FIG. 9 illustrates the formation of passivation layers, metal pads, andoverlying dielectric layers. The respective process is illustrated asstep 214 in the process flow shown in FIG. 21. Passivation layer 72 isformed over dielectric layer 63. Metal pads 74 are formed overpassivation layer 72, and are electrically coupled to RDLs 70. Metalpads 74 may be aluminum pads or aluminum-copper pads, and other metallicmaterials may be used. In accordance with some embodiments of thepresent disclosure, metal pads 74 are not formed, and Post-PassivationInterconnects (PPIs) are formed. Passivation layer 72 may be a singlelayer or a composite layer, and may be formed of a non-porous material.In accordance with some embodiments of the present disclosure,passivation layer 72 is a composite layer including a silicon oxidelayer (not shown separately), and a silicon nitride layer (not shownseparately) over the silicon oxide layer. Passivation layer 72 may alsobe formed of other non-porous dielectric materials such as Un-dopedSilicate Glass (USG), silicon oxynitride, and/or the like. Next, polymerlayer 76 is formed, and then patterned to expose Metal pads 74. Polymerlayer 76 may be formed of polyimide, polybenzoxazole (PBO), or the like.

In accordance with some embodiments of the present disclosure, thestructure underlying Metal pads 74 is free from organic materials (suchas polymer layers), so that the process for forming the structuresunderlying Metal pads 74 may adopt the process used for forming devicedies, and fine-pitches RDLs (such as 66 and 70) having small pitches andline widths are made possible.

Referring to 10, Under-Bump Metallurgies (UBMs) 77 are formed, and UBMs77 extend into polymer layer 76 to connect to metal pads 74 or PPIs. Therespective process is illustrated as step 214 in the process flow shownin FIG. 21. In accordance with some embodiments of the presentdisclosure, each of UBMs 77 includes a barrier layer (not shown) and aseed layer (not shown) over the barrier layer. The barrier layer may bea titanium layer, a titanium nitride layer, a tantalum layer, a tantalumnitride layer, or a layer formed of a titanium alloy or a tantalumalloy. The materials of the seed layer may include copper or a copperalloy. Other metals such as silver, gold, aluminum, palladium, nickel,nickel alloys, tungsten alloys, chromium, chromium alloys, andcombinations thereof may also be included in UBMs 77.

As also shown in FIG. 10, electrical connectors 78 (including 78-1through 78-5) are formed. The respective process is also illustrated asstep 214 in the process flow shown in FIG. 21. An exemplary formationprocess for forming UBMs 77 and electrical connectors 78 includesdepositing a blanket UBM layer, forming and patterning a mask (which maybe a photo resist, not shown), with portions of the blanket UBM layerbeing exposed through the openings in the mask. After the formation ofUBMs 77, the illustrated package is placed into a plating solution (notshown), and a plating step is performed to form electrical connectors 78on UBMs 77. In accordance with some exemplary embodiments of the presentdisclosure, electrical connectors 78 include non-solder parts (notshown), which are not molten in the subsequent reflow processes. Thenon-solder parts may be formed of copper, and hence are referred to ascopper bumps hereinafter, although they may be formed of othernon-solder materials. Each of electrical connectors 78 may also includecap layer(s) (not shown) selected from a nickel layer, a nickel alloy, apalladium layer, a gold layer, a silver layer, or multi-layers thereof.The cap layer(s) are formed over the copper bumps. Electrical connectors78 may further include solder caps. The structure formed in precedingsteps is referred to as composite wafer 80. A die-saw (singulation) stepis performed on composite wafer 80 to separate composite wafer 80 into aplurality of packages 82. The respective process is illustrated as step216 in the process flow shown in FIG. 21.

As shown in FIG. 10, each of passive devices 48 (such as 48A, 48B, 48C,and passive devices 48D through 48G as shown in FIGS. 11 through 13)include two terminals (TA and TB in FIGS. 15 and 16), each electricallyconnecting to one of electrical connectors 78 and one of TSVs 116. Forexample, FIG. 10 illustrates exemplary electrical connectors 78-1, 78-2,78-3, 78-4, and 78-5, which are connected to TSVs 116-1, 116-2, 116-3,64-1, and 64-2, respectively. In accordance with some embodiments of thepresent disclosure, each of passive devices 48A and 48C is electricallyconnected to through-vias 64-1 and 64-2, which are further connected toelectrical connectors 78-4 and 78-5. It is appreciated that one or bothof passive devices 48A and 48C may be formed in accordance with someembodiments. Also, when both passive devices 48A and 48C are formed,passive devices 48A and 48C may be different types of passive devices toform circuits such as LC circuits, RC circuits, RL circuits. Passivedevices 48A and 48C may also be the same types of passive devices suchas capacitors. This may results an increase in the capacitance withoutincreasing the occupied chip area. Similarly, other passive devices suchas passive device 48B are also connected two solder regions (such as78-2 and 78-3).

In accordance with some embodiments of the present disclosure, as shownin FIG. 10, passive devices 48 are formed in package 82, and may be, ormay not be, electrically connected to and used by, the integratedcircuits inside package 82. The two terminals of each of passive devices48 are connected outside of package 82. Accordingly, passive devices 48also have the same function as Surface-Mount Device (SMD), also known asIntegrated Passive Device (IPD). When package 82 is packaged with otherpackage components to form bigger packages, the other package componentsmay access and use the passive devices directly through solder regionsand TSVs.

Referring to FIG. 10 again, TDVs 65 penetrate through isolation regions58, and surround passive device 48. FIG. 17 illustrates a top view of anexemplary layout of TDVs 65, through-vias 64-1 and 64-2, and passivedevice 48. In accordance with some embodiments, a plurality of TDVs 65is formed to encircle through-vias 64-1 and 64-2 and the region directlyunderlying passive device 48 (as shown in FIG. 10). TDVs 65 are close toeach other, for example, with distance D1 smaller than about 10 um. TDVs65 are electrically grounded, and hence form a shielding structure forpreventing the interference between passive device 48 and the integratedcircuit devices that are outside of the regions encircled by TDVs 65.FIG. 18 illustrates a top view of TDV 65 that forms a full ringencircling through-vias 64 and the region directly underlying passivedevice 48.

In accordance with some embodiments of the present disclosure, theregions directly over and direct underlying passive devices 48 are freefrom active devices such as transistors and diodes in order to reducethe interference between passive devices 48 and the integrated circuits.Accordingly, some exclusion zones are designed in device dies 4 and 112,and no active devices are designed in the exclusion zones. Stackingpassive devices and design passive devices in the portions of device die4 that are not overlapped by device die 112 can minimize the requiredexclusion zones.

FIGS. 11 through 13 illustrate some possible locations for formingpassive devices 48. For example, FIG. 11 illustrates that passive device48D is in the metal layers (which may or may not include top metal layerin dielectric layer 32A), and is formed directly under isolation region58. Passive device 48D is connected to through-vias 64-1 and 64-2 andelectrical connectors 78-4 and 78-5.

FIG. 12 illustrates passive devices 48E and 48F. Passive device 48Eincludes the bond pads of device dies 4 and 112, which bond pads arebonded to form the top plates of passive device 48E. The bottom platesand vias (if any) are formed in device die 4. Passive device 48F is inmetal layers (which may or may not include top metal layer in dielectriclayer 32A) in device die 4 and directly under device die 112, and iselectrically connected to TSVs 116-2 and 116-3. Passive device 48D isconnected to through-vias 64-1 and 64-2 and electrical connectors 78-4and 78-5. Passive device 48E includes the bond pads of device dies 4 and112, which bond pads are bonded to form the top plates of passive device48E. The bottom plates and vias (if any) are formed in device die 4.Passive device 48D is also formed directly under isolation region 58.

FIG. 13 illustrates that passive device 48G is in the RDL layersoverlapping device die 112, and are electrically connected to TSVs 116-2and 116-3. Passive device 48G may overlap passive device 48B, and may beconnected in parallel with passive device 48B. It is appreciated thatthe passive devices 48 as shown in FIGS. 10 through 13 may be formed inthe same chip in any combination.

The package shown in FIGS. 1 through 13 has a face-to-face structure, inwhich device dies 112 have their front surfaces facing the front surfaceof device die 4. FIG. 14 illustrates a face-to-back structure, in whichdevice die 112 has its front surface facing the back surface of devicedie 4. Device die 4 includes TSVs 16, which extends through substrate 20and dielectric layer 17. Passive devices 48 are shown as examples. It isappreciated that the passive devices 48 as shown in FIGS. 10 through 13may be formed in the package in FIG. 14 whenever applicable, and thedetails of the passive devices 48 may be essentially the same as inFIGS. 10 through 13, and are not repeated herein.

FIGS. 19 and 20 illustrate the bonding of packages 82 to other packagecomponents. The respective process is illustrated as step 218 in theprocess flow shown in FIG. 21. FIG. 19 illustrates package 84 in whichpackage 82 (FIGS. 10 through 14) is embedded. The package includesmemory cubes 86, which include a plurality of stacked memory dies (notshown separately). Package 82 and memory cubes 86 are encapsulated inencapsulating material 88, which may be a molding compound. Dielectriclayers and RDLs (collectively illustrated as 89) are underlying andconnected to package 82 and memory cubes 86. Passive devices 48 inpackage 82 may be accessed by memory cubes 86 or the package componentsthat are bonded to package 84.

FIG. 20 illustrates Package-on-Package (PoP) structure 90, which hasIntegrated Fan-Out (InFO) package 92 bonded with top package 93. InFOpackage 90 also includes package 82 embedded therein. Package 82 andthrough-vias 94 are encapsulated in encapsulating material 96, which maybe a molding compound. Package 82 is bonded to dielectric layers andRDLs, which are collectively referred to as interconnect structure 95.Passive devices 48 in package 82 (not shown in FIG. 20, refer to FIGS.10 through 14) may be accessed by top package 93 or the packagecomponents that are bonded to package 90.

The embodiments of the present disclosure have some advantageousfeatures. By integrating passive devices in the package, no SMD isneeded, and the manufacturing cost is saved. It is flexible to designthe passive devices in the package.

In accordance with some embodiments of the present disclosure, a methodincludes bonding a first device die with a second device die, whereinthe second device die is over the first device die, and wherein a firstpassive device is formed in a combined structure comprising the firstdevice die and the second device die, and the first passive devicecomprises a first and a second end; filling a gap-filling material overthe first device die, with the gap-filling material comprising portionson opposite sides of the second device die; performing a planarizationto reveal the second device die, with a remaining portion of thegap-filling material forming an isolation region; forming a firstthrough-via and a second through-via penetrating through the isolationregion to electrically couple to the first device die; and forming afirst electrical connector and a second electrical connectorelectrically coupling to the first end and the second end of the firstpassive device. In an embodiment, the first electrical connector and thesecond electrical connector comprise solder regions. In an embodiment,the first end and the second end of the first passive device areconnected to the first through-via and the second through-via,respectively. In an embodiment, the first passive device comprises acapacitor. In an embodiment, the first passive device comprises aninductor. In an embodiment, the first device die comprises a first metalpad, and the second device die comprises a second metal pad bonded tothe first metal pad, and the bonding further results in a second passivedevice to be formed, and the first metal pad and the second metal pad incombination form a plate of the second passive device. In an embodiment,the first device die comprises a first portion of a shielding ring, andthe second device die comprises a second portion of the shielding ring,and the first portion is bonded to the second portion of the shieldingring, and wherein the shielding ring encircles the second passivedevice. In an embodiment, the first device die comprises a third passivedevice comprising a conductive plate, and the gap-filling material is incontact with the conductive plate of the third passive device. In anembodiment, the method further includes forming a plurality ofadditional through-vias in the isolation region, wherein the pluralityof additional through-vias are electrically grounded, and the pluralityof additional through-vias in combination encircle a region directlyunderlying the first passive device.

In accordance with some embodiments of the present disclosure, a methodincludes bonding a first device die with a second device die, whereinfirst metal pads in the first device die are bonded to second metal padsin the second device die; encapsulating the second device die in anisolation region; forming dielectric layers over the second device dieand the isolation region; forming a first passive device in thedielectric layers; and forming a first solder region and a second solderregion over the dielectric layers, wherein the first solder region andthe second solder region are electrically connected to oppositeterminals of the first passive device. In an embodiment, the methodfurther includes etching the isolation region to form a first openingand a second opening; and forming a first through-via and a secondthrough-via in the first opening and the second opening, respectively,wherein the first through-via and the second through-via areelectrically connected to the opposite terminals of the first passivedevice. In an embodiment, the first passive device overlaps theisolation region, and is vertically misaligned from the second devicedie. In an embodiment, the first passive device overlaps the seconddevice die. In an embodiment, the first device die is bonded to thesecond device die through hybrid bonding, and a first surface dielectriclayer of the first device die is bonded to a second surface dielectriclayer of the second device die.

In accordance with some embodiments of the present disclosure, a packageincludes a first device die; a second device die over and bonded to thefirst device die; an isolation region encircling the second device die;a first through-via and a second through-via penetrating through theisolation region to connect respectively to a first bond pad and asecond bond pad in the first device die; and a first passive devicecomprising a first terminal and a second terminal connected to the firstthrough-via and the second through-via, respectively. In an embodiment,the package further includes a first solder region and a second solderregion electrically connected to the first terminal and a secondterminal, respectively, of the first passive device. In an embodiment,the package further includes a second passive device in the first devicedie, wherein terminals of the second passive device are connected to thefirst through-via and the second through-via. In an embodiment, a topplate of the second passive device contacts a bottom surface of theisolation region, and a top surface of the top plate is coplanar with aninterface between the first device die and the second device die. In anembodiment, the first device and the second device are bonded throughhybrid bonding, with bond pads of the first device die bonded to bondpads of the second device die, and a first surface dielectric layer ofthe first device die is bonded to a second surface dielectric layer ofthe second device die, and the second passive device comprises a plateunder the first surface dielectric layer. In an embodiment, the packagefurther includes a shielding structure in the isolation region, whereinthe shielding structure encircles the first through-via and the secondthrough-via.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A package comprising: a first device die; asecond device die over and directly bonded to the first device die; anisolation region encircling the second device die, wherein the isolationregion extends along opposing sidewalls of the second device die; afirst through-via and a second through-via penetrating through theisolation region to contact a first bond pad and a second bond pad,respectively, in the first device die, wherein an interface between thefirst through-via and the first bond pad is level with an interfacebetween the first device die and the second device die; and a firstcapacitor comprising: a first capacitor plate comprising a first portionand a second portion, wherein the first portion is in a first one of thefirst device die and the second device die, wherein the second portionis in a second one of the first device die and the second device die,wherein the second portion is bonded to the first portion; and a secondcapacitor plate in the second one of the first device die and the seconddevice die.
 2. The package of claim 1, wherein the first one of thefirst device die and the second device die is the first device die. 3.The package of claim 1, wherein the first one of the first device dieand the second device die is the second device die.
 4. The package ofclaim 1 further comprising: a second capacitor over both of the seconddevice die and the isolation region.
 5. The package of claim 1 furthercomprising: a first solder region and a second solder region over thesecond device die and electrically connecting to the first through-viaand the second through-via respectively.
 6. The package of claim 1further comprising a second capacitor in the first device die, whereinthe second capacitor comprises a top capacitor plate and a bottomcapacitor plate connecting to the first through-via and the secondthrough-via, respectively.
 7. The package of claim 1, wherein the firstdevice die and the second device die are bonded through hybrid bonding,with first bond pads of the first device die bonded to second bond padsof the second device die, and a first surface dielectric layer of thefirst device die is bonded to a second surface dielectric layer of thesecond device die.
 8. The package of claim 1 further comprising ashielding structure in the isolation region, wherein the shieldingstructure encircles the first through-via and the second through-via. 9.The package of claim 1 further comprising: an etch stop layer disposedbetween the first capacitor plate and the second capacitor plate.
 10. Apackage comprising: a first device die; a second device die over anddirectly bonded to the first device die; an isolation region encirclingthe second device die, wherein the isolation region extends alongopposing sidewalls of the second device die; a first through-via and asecond through-via penetrating through the isolation region to contact afirst bond pad and a second bond pad, respectively, in the first devicedie, wherein an interface between the first through-via and the firstbond pad is level with an interface between the first device die and thesecond device die; a first capacitor comprising: a first capacitor platecomprising a first portion in a first one of the first device die andthe second device die; and a second capacitor plate in a the second oneof the first device die and the second device die; and a secondcapacitor in the first device die, wherein the second capacitorcomprises a top capacitor plate and a bottom capacitor plate connectingto the first through-via and the second through-via, respectively,wherein the top capacitor plate of the second capacitor contacts abottom surface of the isolation region, and a top surface of the topcapacitor plate is coplanar with the interface between the first devicedie and the second device die.
 11. A package comprising: a first devicedie, wherein the first device die comprises: a first surface dielectriclayer; and a first metal feature in the first surface dielectric layer;a second device die over the first device die, wherein the second devicedie comprises: a second surface dielectric layer bonded to the firstsurface dielectric layer; a first dielectric layer, wherein the secondsurface dielectric layer is interposed between the first dielectriclayer and the first device die; and a second metal feature in the secondsurface dielectric layer, wherein the second metal feature is bonded tothe first metal feature; and a passive device comprising: a firstportion in the second device die, wherein the first metal feature andthe second metal feature are in combination a second portion of thepassive device, wherein the first dielectric layer extends between thefirst portion and the first device die.
 12. The package of claim 11,wherein the passive device comprises a capacitor, and the first portionof the capacitor comprises a first capacitor plate of the capacitor, andthe second portion of the capacitor comprises a second capacitor plateof the capacitor.
 13. The package of claim 11, wherein the passivedevice comprises an inductor, and the first portion of the inductorcomprises a first metal plate of the inductor, and the second portion ofthe inductor comprises a second metal plate of the inductor, and theinductor further comprises a via in the second device die, with the viaconnecting the first metal plate to the second metal plate.
 14. Thepackage of claim 11, wherein the first metal feature and the secondmetal feature are bonded to each other through metal-to-metal directbonding.
 15. The package of claim 11 further comprising: an isolationregion encircling the second device die; a first through-via and asecond through-via penetrating through the isolation region; and acapacitor in the first device die, wherein the first through-via and thesecond through-via are electrically connected to capacitor plates of thecapacitor.
 16. A package comprising: a first device die comprising afirst metal feature; and a second device die over and bonded to thefirst device die, wherein the second device die comprises: a secondmetal feature directly bonded to the first metal feature to jointly forma bottom capacitor plate of a capacitor; a dielectric layer over thesecond metal feature, wherein the dielectric layer comprises a portionacting as a capacitor insulator of the capacitor; a top capacitor plate;a semiconductor substrate over the top capacitor plate; and a firstthrough-via and a second through-via penetrating through thesemiconductor substrate, wherein the first through-via and the secondthrough-via are electrically connected to the top capacitor plate andthe bottom capacitor plate, respectively.
 17. The package of claim 16further comprising: an isolation region encircling the second devicedie; an additional dielectric layer over and contacting both of thesecond device die and the isolation region; and a first electricalconnector and a second electrical connector over the dielectric layerand electrically coupling to the capacitor through the first through-viaand the second through-via.
 18. The package of claim 16, wherein firstopposing edges of the first metal feature are flush with correspondingsecond opposing edges of the second metal feature.
 19. The package ofclaim 16, wherein the first device die further comprises active deviceselectrically connecting to the capacitor.
 20. The package of claim 16,wherein the first device die further comprises a first surfacedielectric layer, and the second device die further comprises a secondsurface dielectric layer bonding to the first surface dielectric layerthrough fusion bonding.